The continental margin off the northeastern United States (NEUS) contains numerous,
topographically complex features that increase habitat heterogeneity across the region.
However, the majority of these rugged features have never been surveyed, particularly
using direct observations. During summer 2013, 31 Remotely-Operated Vehicle (ROV)
dives were conducted from 494 to 3271 m depth across a variety of seafloor features to document
communities and to infer geological processes that produced such features. The
ROV surveyed six broad-scale habitat features, consisting of shelf-breaching canyons,
slope-sourced canyons, inter-canyon areas, open-slope/landslide-scar areas, hydrocarbon
seeps, and Mytilus Seamount. Four previously unknown chemosynthetic communities
dominated by Bathymodiolus mussels were documented. Seafloor methane hydrate was
observed at two seep sites. Multivariate analyses indicated that depth and broad-scale habitat
significantly influenced megafaunal coral (58 taxa), demersal fish (69 taxa), and decapod
crustacean (34 taxa) assemblages. Species richness of fishes and crustaceans significantly declined with depth, while there was no relationship between coral richness
and depth. Turnover in assemblage structure occurred on the middle to lower slope at the
approximate boundaries of water masses found previously in the region. Coral species richness
was also an important variable explaining variation in fish and crustacean assemblages.
Coral diversity may serve as an indicator of habitat suitability and variation in
available niche diversity for these taxonomic groups. Our surveys added 24 putative coral
species and three fishes to the known regional fauna, including the black coral Telopathes
magna, the octocoral Metallogorgia melanotrichos and the fishes Gaidropsarus argentatus,
Guttigadus latifrons, and Lepidion guentheri. Marine litter was observed on 81% of the
dives, with at least 12 coral colonies entangled in debris. While initial exploration revealed
the NEUS region to be both geologically dynamic and biologically diverse, further research
into the abiotic conditions and the biotic interactions that influence species abundance and
distribution is needed.